The invention relates to the field of tools for polishing crowns, bridges, dental appliances such as dentures and the like, or jewellery, and more particularly a device which polishes crowns, bridges, dental appliances such as dentures and the like, or jewellery, using an orbital motion.
Currently dental laboratories prepare crowns, bridges and dental appliances such as dentures. After a crown is cast out of gold alloy or porcelain, it is necessary to polish the upper surface of the crown. The upper or functional surface of the crown, like a natural tooth, has a complex convoluted shape or anatomy consisting of convex ridges, concave grooves and a deep central pit. The combination of deep anatomy and projecting ridges is important for the proper functioning of the tooth, and places less stress on the tooth root.
Currently dental laboratories use a lathe for the polishing of the crown or dental appliance. Such lathes use a polishing disc brush made of rigid brushes which is mounted on a rotating shaft. The edge of the rotating disc contacts the surface of the crown. Since the radius of the disc is necessarily too great for the disc to enter the pit, it is generally not possible to polish the depth of the pit without wearing down the surrounding anatomy. Similarly the disc cannot reach all parts of the grooves and ridges without wearing down the anatomy of the crown, which is undesirable. There is therefore a need for a device for polishing crowns, bridges or dental appliances which preserves the anatomy of the crown.
The present invention provides a device for polishing a workpiece having a convoluted surface comprising: a brush-supporting member; an electric motor for imparting an orbital motion to the brush-supporting member; and a polishing brush comprising a curved working surface mounted on the brush-supporting member. According to one aspect, the brush has a hemispherical face. The hemispherical face preferably faces vertically downwardly. The device may have a horizontal base, and may comprise a vertical motor support. The motor may be mounted within a motor housing on said vertical motor support. Preferably the brush-supporting plate extends downwardly from said motor housing and the device preferably has a plurality of brushes mounted on said brush-supporting plate.